That's ok for me, but I thought that things work by default.

The real problem is mentioned here: https://wiki.freebsd.org/BjoernZeeb/Ten64

If loaded as module from multi-user we do not get the time set even if manually triggering a sysctl debug.clock_do_io=1. Reason for this is that vfs_moutroot() is responsible to have the clock set and calls CLOCK_GETTIME() indirectly so that log files or other timestamps do not appear to go backwards (if no RTC is found it'll use the vfs root node date?). Look for the inittodr() call.